What is meant by the temperature rise of a motor and how does it apply?
A – It is the difference between the measured temperature of the motor winding and the temperature of the air surrounding the motor. Electrical insulation systems are limited in the degree of temperature that they can withstand. Standard motors have Class “A” insulation systems, which are rated at 105C for the hottest-spot temperature. A hot-spot allowance must be made for the difference between the measured temperature of the winding and the actual temperature of the hottest-spot within the winding, usually 5C to 15C depending upon the type of motor construction. The sum of the temperature rise, the hot-spot allowance, and the temperature of the ambient must not exceed the temperature rating of the insulation.
